Method for producing group III nitride semiconductor light-emitting device

ABSTRACT

The present techniques provide a method for producing a Group III nitride semiconductor light-emitting device, with suppression of an increase in polarity inversion defect density. The production method includes an n-type semiconductor layer formation step, a light-emitting layer formation step, and a p-type semiconductor layer formation step. The p-type semiconductor layer formation step includes a p-type cladding layer formation step. The p-type cladding layer formation step includes a first p-type semiconductor layer formation step for forming a p-type AlGaN layer, a first semiconductor layer growth intermission step after the first p-type semiconductor layer formation step, and a p-type InGaN layer formation step after the first semiconductor layer growth intermission step. In the first semiconductor layer growth intermission step, a mixture of nitrogen gas and hydrogen gas is supplied to the substrate.

BACKGROUND OF THE INVENTION

Field of the Invention

The present techniques relate to a method for producing a Group IIInitride semiconductor light-emitting device. More particularly, thetechniques relate to a method for producing a Group III nitridesemiconductor light-emitting device, which can provide a p-type claddinglayer having high crystallinity.

Background Art

Group III nitride semiconductor crystals are produced through vaporphase growth techniques such as metal organic chemical vapor deposition(MOCVD) or hydride vapor phase epitaxy (HVPE); molecular-beam epitaxy(MBE); pulsed sputter deposition (PSD); liquid phase epitaxy (LPE); or asimilar technique.

Among these techniques, when semiconductor layers are grown by MOCVD,various gases are fed to an MOCVD furnace, and the semiconductor layeris formed in the atmosphere of the furnace. Patent Document 1 disclosesa technique for growth of a semiconductor layer, wherein

a nitrogen gas atmosphere and a nitrogen-hydrogen gas mixture atmosphereare selectively employed, depending on the composition of thesemiconductor layer to be formed. (see Patent Document 1, paragraph[0107]).

Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.2013-175790

Meanwhile, polarity inversion defects may be generated in a Group IIInitride semiconductor layer during growth thereof. A polarity inversiondefect refers to a defect caused by intermingling of an N-plane with aGa-plane. The number of polarity inversion defects per unit area of aplane orthogonal to the direction of growth of the semiconductor layeris defined as “polarity inversion defect density.” The lower thepolarity inversion defect density, the higher the crystallinity of thesemiconductor layer.

Generally, the polarity inversion defect density increases with theprogress of epitaxial growth. In other words, the polarity inversiondefect density at the later stage of epitaxial growth is generallyhigher than that at the initial stage of epitaxial growth. Thus,suppression of an increase in polarity inversion defect density in thecourse of epitaxial growth is preferable.

In a growth atmosphere containing hydrogen gas, some semiconductorlayers may be damaged during growth thereof. Thus, it is preferred thatan increase in polarity inversion defect density is suppressed, withoutdegradation of the crystallinity of the semiconductor layer duringgrowth.

SUMMARY OF THE INVENTION

The present techniques have been conceived in order to solve theaforementioned problems. Thus, an object of the present techniques is toprovide a method for producing a Group III nitride semiconductorlight-emitting device, which suppresses an increase in polarityinversion defect density.

In a first aspect of the present techniques, there is provided a methodfor producing a Group III nitride semiconductor light-emitting device,the method comprising: (a) forming an n-type semiconductor layer on asubstrate; (b) forming a light-emitting layer on the n-typesemiconductor layer; and (c) forming a p-type semiconductor layer on thelight-emitting layer. The step (c) comprises a step (d) forming a p-typecladding layer, the step (d) comprising: (e) forming a first p-typesemiconductor layer; (f) interrupting a semiconductor layer growth afterforming the first p-type semiconductor layer; and (g) forming a p-typeInGaN layer after the interruption, in the step (f), a mixture ofnitrogen gas and hydrogen gas is supplied to the substrate.

In the method for producing a Group III nitride semiconductorlight-emitting device, the mixture of nitrogen gas and hydrogen gas issupplied to the substrate, not in the growth phase in which raw materialgases for forming a semiconductor layer are supplied but in theintermission phase in which supply of at least one raw material gas ispaused. The semiconductor layer can be etched by hydrogen gas. Sincebonding strength between atoms is weak in polarity inversion defects, asemiconductor layer having such defects is readily etched. Thus, aftergrowth of the first p-type semiconductor layer, polarity inversiondefects present on the surface of the first p-type semiconductor layerare preferentially etched. Thus, after the first intermission phase,polarity inversion defects on the first p-type semiconductor layerdecrease to some extent. As a result, in a semiconductor light-emittingdevice produced through the method, a polarity inversion defect densityin the p-type semiconductor layer is lower than that of a conventionalsemiconductor light-emitting device.

In the production method of the techniques, different carrier gases areemployed in the semiconductor layer formation step and the semiconductorlayer growth intermission step. Also, hydrogen gas is supplied beforeformation of the p-type InGaN layer, whereby polarity inversion defectson the surface of the p-type semiconductor layer are decreased. As aresult, the p-type InGaN layer receives substantially no damage.

In a second aspect of the present techniques, there is provided a methodfor producing a Group III nitride semiconductor light-emitting device,the step (d) further comprising: (h) interrupting a semiconductor layergrowth after forming the p-type InGaN layer, in the step (h), nitrogengas is supplied to the substrate, while no hydrogen gas is supplied tothe substrate.

In a third aspect of the present techniques, there is provided a methodfor producing a Group III nitride semiconductor light-emitting device,in the first p-type semiconductor layer formation step and the p-typeInGaN layer formation step, nitrogen gas is supplied to the substrate,while no hydrogen gas is supplied to the substrate.

In a fourth aspect of the present techniques, there is provided a methodfor producing a Group III nitride semiconductor light-emitting device,the ratio of the volume of hydrogen gas to the total volume of nitrogengas and hydrogen gas of the gas mixture is adjusted to 20% to 100%, inthe first intermission step. When the volume ratio falls within therange, low polarity inversion defect density can be attained.

In a fifth aspect of the present techniques, there is provided a methodfor producing a Group III nitride semiconductor light-emitting device,in the first p-type semiconductor layer formation step, a p-type AlGaNlayer or a p-type GaN layer is formed as the first p-type semiconductorlayer.

The present techniques enable provision of a method for producing aGroup III nitride semiconductor light-emitting device, with suppressionof an increase in polarity inversion defect density.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other objects, features, and many of the attendant advantages ofthe present techniques will be readily appreciated as the same becomesbetter understood with reference to the following detailed descriptionof the preferred embodiments when considered in connection with theaccompanying drawings, in which:

FIG. 1 is a schematic view of a Group III nitride semiconductorlight-emitting device according to an embodiment;

FIG. 2 is a layer structure of the Group III nitride semiconductorlight-emitting device according to the embodiment, mainly focused on thep-type cladding layer;

FIG. 3 is a graph describing a p-type cladding layer production stepincluded in the method for producing the Group III nitride semiconductorlight-emitting device of the embodiment;

FIG. 4 is a schematic view for describing a production step for theGroup III nitride semiconductor light-emitting device according to theembodiment (No. 1);

FIG. 5 is a schematic view for describing a production step for theGroup III nitride semiconductor light-emitting device according to theembodiment (No. 2);

FIG. 6 is a graph showing the relationship between the hydrogen contentof the gas mixture supplied in the first intermission phase of thep-type cladding layer formation step and the polarity inversion defectdensity; and

FIG. 7 is a graph showing the relationship between the forward currentand the drive voltage, in the presence or absence of hydrogen gas in thegas supplied in the first intermission phase of the p-type claddinglayer formation step.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A specific embodiment of the semiconductor light-emitting device and theproduction method therefor will next be described, with reference to thedrawings. However, the embodiment should not be construed as limitingthe techniques thereto. The layer structure of the below-describedsemiconductor light-emitting device and the electrode configurationthereof are merely examples, and a layer structure other than that ofthe embodiment may also be employed. The thickness of each of the layersshown in the drawings is a conceptual thickness, which is not an actualthickness.

1. Semiconductor Light-Emitting Device

FIG. 1 shows a general structure of a light-emitting device 100according to the embodiment. The light-emitting device 100 is a face-uptype semiconductor light-emitting device. The light-emitting device 100has semiconductor layers Ep1 composed of a plurality of Group IIInitride semiconductor layers.

As shown in FIG. 1, the light-emitting device 100 has a substrate 110,the semiconductor layer Ep1, a transparent electrode 190, an n-electrodeN1, and a p-electrode P1. The semiconductor layer Ep1 includes alow-temperature buffer layer 120, an n-type contact layer 130, an n-typehigh breakdown voltage layer 140, an n-type cladding layer 150, alight-emitting layer 160, a p-type cladding layer 170, and a p-typecontact layer 180. The n-type contact layer 130, the n-type highbreakdown voltage layer 140, and the n-type cladding layer 150 are madeof an n-type semiconductor. The p-type cladding layer 170 and the p-typecontact layer 180 are made of a p-type semiconductor. The n-typesemiconductor layers and the p-type semiconductor layers may include anon-doped semiconductor layer. The light-emitting device 100 may have aprotective film for protecting a semiconductor layer Ep1 or the like.

The low-temperature buffer layer 120 is disposed on a main surface ofthe substrate 110. The low-temperature buffer layer 120 is made of amaterial such as AlN or GaN. The n-type contact layer 130 is disposed onthe low-temperature buffer layer 120. The n-type contact layer 130 ismade of a material such as n-type GaN. The n-type high breakdown voltagelayer 140 is disposed on the n-type contact layer 130. The n-type highbreakdown voltage layer 140 serves as a layer which preventselectrostatic breakdown of the semiconductor layer Ep1. The n-type highbreakdown voltage layer 140 is formed of, for example, a depositedstructure of a non-doped GaN layer and an n-type GaN layer. The n-typecladding layer 150 is disposed on the n-type high breakdown voltagelayer 140. The n-type cladding layer 150 serves as a strain relaxationlayer for relaxing the stress applied to the light-emitting layer 160.The n-type cladding layer 150 is a super-lattice layer having asuper-lattice structure. The n-type cladding layer 150 is formed of, forexample, a super-lattice structure of n-type GaN layers and n-type InGaNlayers.

The light-emitting layer 160 is disposed on the n-type cladding layer150. In the light-emitting layer 160, holes and electrons are recombinedto cause light emission. The p-type cladding layer 170 is disposed onthe light-emitting layer 160. The p-type cladding layer 170 is asuper-lattice layer having a super-lattice structure. The p-type contactlayer 180 is disposed on the p-type cladding layer 170.

The transparent electrode 190 is disposed on the p-type contact layer180. The transparent electrode 190 is preferably made of any materialselected from among ITO, IZO, ICO, ZnO, TiO₂, NbTiO₂, TaTiO₂, and SnO₂.

The n-electrode N1 is disposed on the n-type contact layer 130. Then-electrode N1 is a deposited structure of an Ni layer and an Au layer,with the Ni layer being in contact with the n-type contact layer 130.The n-electrode N1 may be a deposited structure formed by sequentiallydepositing V, Al or Ti, and Al. The p-electrode P1 is disposed on thetransparent electrode 190. The p-electrode P1 is a deposited structureof an Ni layer and an Au layer, with the Ni layer being in contact withthe transparent electrode 190.

2. The Layer Structure in the Vicinity of the p-Type Cladding Layer 2-1.Light-Emitting Layer

FIG. 2 is a schematic view of a layer structure including thelight-emitting layer 160 and the p-type cladding layer 170. In thelight-emitting layer 160, holes and electrons are recombined to causelight emission. The light-emitting layer 160 has a multiple quantum well(MQW) structure in which unit layer structures are repeatedly deposited.Each unit layer structure is formed of an InGaN layer 161, a GaN layer162, and an AlGaN layer 163, which are deposited in this order on theunder layer. In one mode, nine unit layer structures are repeatedlydeposited. The number of repetition may be varied within the range of 5to 12. Needless to say, the number of repetition may fall outside therange. Also, the deposit order of the layers in the unit layer structuremay be altered. Any unit layer structure, other than the aforementionedone, may also be employed. In such a case, GaN, InGaN, AlGaN, andAlInGaN may be combined at random.

2-2. p-Type Cladding Layer

The p-type cladding layer 170 is disposed on the light-emitting layer160. The p-type cladding layer 170 is formed by repeatedly depositing ap-type AlGaN layer 171 and a p-type InGaN layer 172. The number ofrepetition is, for example, five. Each p-type AlGaN layer 171 has an Alcontent (compositional proportion) of 10% to 40%. The p-type AlGaN layer171 has a thickness of 5 Å to 70 Å. Each p-type InGaN layer 172 has anIn content (compositional proportion) of 2% to 20%. Notably, the Incontent of the p-type InGaN layer 172 is smaller than that of the InGaNlayer 161 of the light-emitting layer 160. The p-type InGaN layer 172has a thickness of 5 Å to 70 Å. These content and thickness values aremerely examples, and other values may be acceptable. The p-type claddinglayer may have another layer configuration.

2-3. p-Type Contact Layer

The p-type contact layer 180 is disposed on the p-type cladding layer170. The p-type contact layer 180 is made of a material such as p-typeGaN. The p-type contact layer 180 may have a double-layer structure oftwo layers having different carrier concentrations.

3. p-Type Cladding Layer Production Step 3-1. Production Step

A production step for producing a p-type cladding layer 170 will next bedescribed. FIG. 3 is a graph describing the production step for thep-type cladding layer 170. As shown in FIG. 3, the production step forthe p-type cladding layer 170 includes a first p-type semiconductorlayer formation step, a first intermission step, a p-type InGaN layerformation step, and a second intermission step.

In the first p-type semiconductor layer formation step, a p-type AlGaNlayer 171 is formed. In the first intermission step, semiconductor layergrowth is stopped after the first p-type semiconductor layer formationstep. In the p-type InGaN layer formation step, a p-type InGaN layer 172is formed after the first intermission step. In the second intermissionstep, semiconductor layer growth is stopped after the p-type InGaN layerformation step. After the second intermission step, the first p-typesemiconductor layer formation step is carried out, whereby anotherp-type AlGaN layer 171 and another p-type InGaN layer 172 are repeatedlydeposited.

FIG. 3 shows a first film formation phase T1 for forming the p-typeAlGaN layer 171, a first intermission phase T2 in which film formationis stopped after formation of the p-type AlGaN layer 171, a second filmformation phase T3 for forming the p-type InGaN layer 172, and a secondintermission phase T4 in which film formation is stopped after formationof the p-type InGaN layer 172. The first intermission phase T2 isdefined as a period of time from termination of formation of the p-typeAlGaN layer 171 to initiation of formation of the p-type InGaN layer172. The second intermission phase T4 is defined as a period of timefrom termination of formation of the p-type InGaN layer 172 toinitiation of formation of the p-type AlGaN layer 171.

As shown in FIG. 3, in the first film formation phase T1, no hydrogengas is supplied, but nitrogen gas is supplied to the MOCVD furnace. As aresult, nitrogen gas is selectively supplied to the substrate 110,without supplying hydrogen gas to the substrate 110. The substratetemperature in the first layer formation phase T1 is 800° C. to 1,050°C.

In the first intermission phase T2, a mixture of nitrogen gas andhydrogen gas is supplied. The gas mixture will be described in detailhereinafter. In the first intermission phase T2, the substratetemperature is lowered from the temperature employed in the first layerformation phase T1 to that of the second layer formation phase T3. Thus,in the first intermission phase T2, a mixture of nitrogen gas andhydrogen gas is supplied, while the substrate temperature is lowered.

In the second layer formation phase T3, nitrogen gas is supplied to thesubstrate 110, without supplying hydrogen gas to the substrate 110. Thesubstrate temperature in the second film formation phase T3 is 700° C.to 950° C.

In the second intermission phase T4, nitrogen gas is supplied to thesubstrate 110, without supplying hydrogen gas to the substrate 110. Inthe second intermission phase T4, the substrate temperature is elevatedfrom the temperature employed in the second film formation phase T3 tothat of the first film formation phase T1.

3-2. Gas Mixture Used in the First Intermission Step

In the first intermission step, the ratio X of the volume of hydrogengas to the total volume of nitrogen gas and hydrogen gas of the gasmixture (hereinafter referred to as “hydrogen gas mixing ratio”) isadjusted to 20% to 100%. The hydrogen gas mixing ratio X satisfies thefollowing condition:X=VH ₂/(VH ₂ +VN ₂)VH₂: volume of hydrogen gasVN₂: volume of nitrogen gas

The hydrogen gas mixing ratio X is preferably 40% to 95%, morepreferably 50% to 80%. The range of hydrogen gas mixing ratio X will bedescribed in detail hereinafter.

3-3. Polarity Inversion Defect Density

When a semiconductor layer is formed through epitaxial growth on aGa-plane side surface, in some case an N-plane is intermingled with theGroup III element-plane. The thus-formed N-plane-incorporated sites arereferred to as polarity inversion defects, and the number of polarityinversion defects per unit area is defined as “polarity inversion defectdensity.” The polarity inversion defect density tends to increase as theprogress of epitaxial growth. That is, the polarity inversion defectdensity at the later stage of epitaxial growth is generally higher thanthat at the initial stage of epitaxial growth.

In this embodiment, a mixture of nitrogen gas and hydrogen gas issupplied to the epitaxial growth layer in the first intermission phaseT2. The epitaxial growth layer is etched by supplied hydrogen gas. Aportion including polarity inversion defects is more susceptible toetching. That is, in the production method, polarity inversion defectsare preferentially etched.

In this embodiment, no hydrogen gas is supplied to the growth chamber inthe second intermission phase T4. Thus, etching of the p-type InGaNlayer 172 of the p-type cladding layer 170 by hydrogen gas issubstantially prevented. As a result, the surface of the p-type InGaNlayer 172 is not damaged.

As described above, in the embodiment of the production method, polarityinversion defects are preferentially removed through etching from thesurface of the p-type AlGaN layer 171 of the p-type cladding layer 170,whereby rise in polarity inversion defect density can be suppressed. Inthis embodiment, supply of hydrogen gas is stopped, and then the p-typeInGaN layer 172 is formed. As a result, damage of the p-type InGaN layer172 of the p-type cladding layer 170 by hydrogen gas is prevented.

4. Semiconductor Light-Emitting Device Production Method

Next will be described an embodiment of the method for producing thesemiconductor light-emitting device. The production method includes:

forming an n-type semiconductor layer on a substrate,

forming a light-emitting layer on the n-type semiconductor layer, and

forming a p-type semiconductor layer on the light-emitting layer.

In this production method, semiconductor layers are formed throughepitaxial growth on a substrate 110. Epitaxial growth is carried out bymetal organic chemical vapor deposition (MOCVD). The carrier gasemployed in the method is hydrogen gas (H₂), nitrogen gas (N₂), or amixture of hydrogen gas and nitrogen gas (H₂+N₂). The nitrogen gassource may be ammonia gas (NH₃). The Ga source may be trimethylgallium(Ga(CH₃)₃: hereinafter abbreviated as “TMG”). The In source may betrimethylindium (In(CH₃)₃: hereinafter abbreviated as “TMI”). The Alsource may be trimethylaluminum (Al(CH₃)₃: hereinafter abbreviated as“TMA”). Silane (SiH₄) may be used as an n-type dopant gas.Cyclopentadienylmagnesium (Mg(C₅H₅)₂: hereinafter referred to as“Cp₂Mg”) may be used as a p-type dopant gas.

4-1. n-Type Semiconductor Layer Formation Step 4-1-1. n-Type ContactLayer Formation Step

Firstly, a low-temperature buffer layer 120 is formed on the substrate110. An n-type contact layer 130 is formed on the low-temperature bufferlayer 120. The substrate temperature is, for example, 1,080° C. to1,140° C.

4-1-2. n-Type High Breakdown Voltage Layer Formation Step

Subsequently, an n-type high breakdown voltage layer 140 is formed onthe n-type contact layer 130. The substrate temperature is, for example,750° C. to 950° C.

4-1-3. n-Type Cladding Layer Formation Step

Then, an n-type cladding layer 150 is formed on the n-type highbreakdown voltage layer 140. The substrate temperature is, for example,700° C. to 950° C.

4-2. Light-Emitting Layer Formation Step

Next, a light-emitting layer 160 is formed on the n-type cladding layer150. The light-emitting layer 160 is formed through repeatedlydepositing layer structure units, and the number of depositing isdescribed above. The layer structure unit is formed by depositing anInGaN layer, a GaN layer, and an AlGaN layer in this order from theunder layer. The InGaN layer is formed at a growth temperature of 750°C. to 800° C. by supplying raw material gases of TMI, TMG, and ammonia.The AlGaN layer is formed at a growth temperature of 850° C. to 950° C.by supplying raw material gases of TMA, TMG, and ammonia.

4-3. p-Type Semiconductor Layer Formation Step 4-3-1. p-Type CladdingLayer Formation Step

On the light-emitting layer 160, a p-type cladding layer 170 is formed.As described above, the first p-type semiconductor layer formation step,the first intermission step, the p-type InGaN layer formation step, andthe second intermission step are carried out. In the first p-typesemiconductor layer formation step, CP₂Mg, TMA, TMG, and ammonia aresupplied for forming a p-type AlGaN layer 171.

In the first intermission step, a mixture of nitrogen gas and hydrogengas is supplied to the substrate 110, while the substrate temperature islowered. Specifically, supply of hydrogen gas is initiated at the startof the first intermission step, and terminated at the end of the firstintermission step. During the first intermission step, the substratetemperature is lowered. Thus, in the first intermission phase T2 of thefirst intermission step, hydrogen gas is supplied to the growth chamberwhile the substrate temperature is lowered.

In the p-type InGaN layer formation step, CP₂Mg, TMI, TMG, and ammoniaare supplied for forming a p-type InGaN layer 172. In secondintermission step, nitrogen gas is supplied to the substrate 110 whilethe substrate temperature is elevated.

4-3-2. p-Type Contact Layer Formation Step

Subsequently, a p-type contact layer 180 is formed on the p-typecladding layer 170. The substrate temperature is, for example, 900° C.to 1,050° C. FIG. 4 shows the layer structure after formation of thep-type contact layer 180.

4-4. Transparent Electrode Formation Step

On the p-type contact layer 180, a transparent electrode 190 is formedthrough sputtering or a similar technique. The transparent electrode 190is formed on an area other than an area where an n-electrode N1 is to beformed.

4-5. Electrode Formation Step

Subsequently, the p-type contact layer 180 is dry-etched from the topsurface thereof, whereby a groove reaching the intermediate depth of then-type contact layer 130 is provided. As shown FIG. 5, a part of then-type contact layer 130 is exposed. On the thus-exposed n-type contactlayer 130, the n-electrode N1 is formed. Also, a p-electrode P1 isformed on the transparent electrode 190.

4-6. Device Chipping Step

The substrate 110 on which the semiconductor layers and the electrodeshave been provided is cut to individual devices. Device chipping isperformed by means of a laser cutting apparatus or a breaking apparatus.

4-7. Other Steps

In addition to the aforementioned steps, there may be further performeda protective film formation step, a thermal treatment step forsemiconductor layers, and other steps. Through such steps, thelight-emitting device 100 shown in FIG. 1 is produced.

5. Experiments 5-1. Polarity Inversion Defect Density

Some experiments were carried out to assess the formed p-type claddinglayer 170. In the first experiment, the p-type cladding layer 170 wasformed under variation of the hydrogen mixing ratio X in the firstintermission step. At each hydrogen mixing ratio X, polarity inversiondefect density was determined. The polarity inversion defect density wasmeasured at the interface between the p-type cladding layer 170 and thep-type contact layer 180. Separately, a light-emitting device 100 wasfabricated using the present techniques, and drive voltage was measured.

FIG. 6 is a graph showing the relationship between the hydrogen contentX and the polarity inversion defect density, under variation of X. InFIG. 6, the horizontal axis represents hydrogen gas mixing ratio X, andthe vertical axis represents polarity inversion defect density. As shownin FIG. 6, when hydrogen gas was present in the first intermission phaseT2, polarity inversion defect density was low.

Specifically, when the hydrogen gas mixing ratio X was 20% to 100%(denoted by arrow L1 in FIG. 6), the polarity inversion defect densitywas 1.2×10⁹ cm⁻² or lower. When the hydrogen gas mixing ratio X was 40%to 95% (denoted by arrow L2 in FIG. 6), the polarity inversion defectdensity was 9.0×10⁸ cm⁻² or lower. When the hydrogen gas mixing ratio Xwas 50% to 80% (denoted by arrow L3 in FIG. 6), the polarity inversiondefect density was 8.0×10⁸ cm⁻² or lower.

As described above, the hydrogen gas mixing ratio X of the gas mixtureis preferably 20% to 100%, more preferably 40% to 95%, still morepreferably 50% to 80%.

5-2. Drive Voltage

A light-emitting device was fabricated when a mixture of nitrogen gasand hydrogen gas was used in the first intermission step involved in thep-type cladding layer formation step (Example). Another light-emittingdevice was fabricated when nitrogen gas was used with no hydrogen gas(Comparative Example). The two light-emitting devices were compared witheach other in terms of drive voltage.

FIG. 7 is a graph showing the relationship between drive voltage Vf andforward current If. As shown in FIG. 7, the light-emitting devicefabricated with a mixture of nitrogen gas and hydrogen gas (Example) wasfound to exhibit a drive voltage lower than that of the light-emittingdevice fabricated with nitrogen gas (Comparative Example).

More specifically, as shown in TABLE 1, the light-emitting devicefabricated with a mixture containing hydrogen gas exhibited a drivevoltage of 4.08 V when the forward current If was 1000 mA. Thelight-emitting device fabricated without supply of hydrogen gasexhibited a drive voltage of 4.13 V when the forward current If was 1000mA. When the forward current If was 2000 mA, the light-emitting devicefabricated with a mixture containing hydrogen gas exhibited a drivevoltage of 4.87 V, and the light-emitting device fabricated withoutsupply of hydrogen gas exhibited a drive voltage of 4.93 V.

TABLE 1 If Vf (with no hydrogen) Vf (with hydrogen) 1000 mA 4.13 V 4.08V 2000 mA 4.93 V 4.87 V

As is clear from TABLE, the polarity inversion defect density of thep-type AlGaN layer 171 can be reduced through supplying a mixture ofnitrogen gas and hydrogen gas during the first intermission phase T2.Thus, the polarity inversion defect density of a subsequently grownsemiconductor layer becomes lower than that of a similar layer employedin a conventional semiconductor light-emitting device. The drive voltageVf of the light-emitting device 100 of the above embodiment is low.

6. Modifications 6-1. p-Type Cladding Layer

In the above embodiment, a p-type AlGaN layer 171 is employed in thep-type cladding layer 170. Alternatively, a p-type GaN layer may beemployed instead of the p-type AlGaN layer 171.

6-2. Order of Layer Formation in p-Type Cladding Layer

In the above embodiment, the p-type AlGaN layer 171 and the p-type InGaNlayer 172 are sequentially formed. Alternatively, the p-type InGaN layermay be formed first. Even in the alternative case, a mixture of hydrogengas and nitrogen gas is supplied during the intermission phase afterformation of the p-type AlGaN layer.

6-3. Gas Mixture

In addition to the aforementioned gas mixture, an additional gas such asammonia may be supplied during the first intermission step afterformation of the p-type cladding layer.

6-4. Combination

The aforementioned modifications may be employed in combinationarbitrarily.

7. Summary of the Embodiment

As described hereinabove, in the embodiment of the method for producinga Group III nitride semiconductor light-emitting device, a mixture ofhydrogen gas and nitrogen gas is supplied in the first intermission stepT2 involved in the p-type cladding layer formation step. Thus, thepolarity inversion defects in the surface of the p-type AlGaN layer 171can be reduced, whereby the light-emitting device 100 ensures low drivevoltage Vf.

The above embodiment is merely an example, and the present techniquesmay encompass various modifications and variations, so long as they fallwithin the scope of the present techniques. In the above embodiment,metal organic chemical vapor deposition (MOCVD) is employed as anepitaxial growth technique. However, other vapor phase growth techniquessuch as hydride vapor phase epitaxy (HVPE) may also be employed.

8. Note

In the first intermission step, a mixture of hydrogen gas and nitrogengas is supplied, while the substrate temperature is lowered. At theinitiation of the first intermission step, supply of hydrogen gas isstarted, and supply of hydrogen is stopped at the termination of thefirst intermission step.

What is claimed is:
 1. A method for producing a Group III nitridesemiconductor light-emitting device, the method comprising: forming ann-type semiconductor layer on a substrate; forming a light-emittinglayer on the n-type semiconductor layer; forming a p-type cladding layeron the light-emitting layer, and forming a p-type contact layer on thep-type cladding layer; the forming of the p-type cladding layercomprising: forming a first p-type semiconductor layer; interrupting asemiconductor layer growth after the forming of the first p-typesemiconductor layer; and forming a p-type InGaN layer after theinterrupting of the semiconductor layer growth, wherein the interruptingof the semiconductor layer growth after the forming of the first p-typesemiconductor layer comprises, supplying a mixture of nitrogen gas andhydrogen gas to the substrate, and etching at least polarity inversiondefects of a surface of the first p-type semiconductor layer.
 2. Themethod for producing a Group III nitride semiconductor light-emittingdevice according to claim 1, the forming of the p-type cladding layerfurther comprising: interrupting a semiconductor layer growth after theforming of the p-type InGaN layer, wherein in the interrupting of thesemiconductor layer growth after the forming of the p-type InGaN layer,nitrogen gas is supplied to the substrate, while no hydrogen gas issupplied to the substrate.
 3. The method for producing a Group IIInitride semiconductor light-emitting device according to claim 2,wherein in the forming of the first p-type semiconductor layer and theforming of the p-type InGaN layer, nitrogen gas is supplied to thesubstrate, while no hydrogen gas is supplied to the substrate.
 4. Themethod for producing a Group III nitride semiconductor light-emittingdevice according to claim 3, wherein the ratio of the volume of hydrogengas to the total volume of nitrogen gas and hydrogen gas of the gasmixture is adjusted to 20% to 100%, in the interrupting of thesemiconductor layer growth after the forming of the first p-typesemiconductor layer.
 5. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 3, the forming ofthe first p-type semiconductor layer further comprising: forming ap-type AlGaN layer or a p-type GaN layer as the first p-typesemiconductor layer.
 6. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 2, wherein theratio of the volume of hydrogen gas to the total volume of nitrogen gasand hydrogen gas of the gas mixture is adjusted to 20% to 100%, in theinterrupting of the semiconductor layer growth after the forming of thefirst p-type semiconductor layer.
 7. The method for producing a GroupIII nitride semiconductor light-emitting device according to claim 2,the forming of the first p-type semiconductor layer further comprising:forming a p-type AlGaN layer or a p-type GaN layer as the first p-typesemiconductor layer.
 8. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 2, in theinterrupting of the semiconductor layer growth after the forming of thefirst p-type semiconductor layer: lowering the substrate temperature;starting a supply of hydrogen gas at an initiation of the interruptingof the semiconductor layer growth after the forming of the first p-typesemiconductor layer; and stopping the supply of hydrogen gas at atermination of the interrupting of the semiconductor layer growth afterthe forming of the first p-type semiconductor layer.
 9. The method forproducing a Group III nitride semiconductor light-emitting deviceaccording to claim 2, wherein the forming of the p-type cladding layercomprises depositing the first p-type semiconductor layer and the p-typeInGaN layer repeatedly.
 10. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 1, wherein in theforming of the first p-type semiconductor layer and the forming of thep-type InGaN layer, nitrogen gas is supplied to the substrate, while nohydrogen gas is supplied to the substrate.
 11. The method for producinga Group III nitride semiconductor light-emitting device according toclaim 10, wherein the ratio of the volume of hydrogen gas to the totalvolume of nitrogen gas and hydrogen gas of the gas mixture is adjustedto 20% to 100%, in the interrupting of the semiconductor layer growthafter the forming of the first p-type semiconductor layer.
 12. Themethod for producing a Group III nitride semiconductor light-emittingdevice according to claim 10, the forming of the first p-typesemiconductor layer further comprising: forming a p-type AlGaN layer ora p-type GaN layer as the first p-type semiconductor layer.
 13. Themethod for producing a Group III nitride semiconductor light-emittingdevice according to claim 1, wherein the ratio of the volume of hydrogengas to the total volume of nitrogen gas and hydrogen gas of the gasmixture is adjusted to 20% to 100%, in the interrupting of thesemiconductor layer growth after the forming of the first p-typesemiconductor layer.
 14. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 1, the forming ofthe first p-type semiconductor layer further comprising: forming ap-type AlGaN layer or a p-type GaN layer as the first p-typesemiconductor layer.
 15. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 1, in theinterrupting of the semiconductor layer growth after the forming of thefirst p-type semiconductor layer: lowering the substrate temperature;starting a supply of hydrogen gas at an initiation of the interruptingof the semiconductor layer growth after the forming of the first p-typesemiconductor layer; and stopping the supply of hydrogen gas at atermination of the interrupting of the semiconductor layer growth afterthe forming of the first p-type semiconductor layer.
 16. The method forproducing a Group III nitride semiconductor light-emitting deviceaccording to claim 1, wherein the forming of the p-type cladding layercomprises depositing the first p-type semiconductor layer and the p-typeInGaN layer repeatedly.
 17. The method for producing a Group III nitridesemiconductor light-emitting device according to claim 1, wherein in theforming of the first p-type semiconductor layer, a temperature of thesubstrate is in a range from 800° C. to 1,050° C.
 18. The method forproducing a Group III nitride semiconductor light-emitting deviceaccording to claim 1, wherein in the forming of the p-type InGaN layer,a temperature of the substrate is in a range from 700° C. to 950° C. 19.A method for producing a Group III nitride semiconductor light-emittingdevice, the method comprising: forming an n-type semiconductor layer ona substrate; forming a light-emitting layer on the n-type semiconductorlayer; forming a p-type cladding layer on the light-emitting layer, andforming a p-type contact layer on the p-type cladding layer; wherein theforming of the p-type cladding layer comprises: forming a first p-typesemiconductor layer; interrupting a semiconductor layer growth after theforming of the first p-type semiconductor layer; and forming a p-typeInGaN layer after the interrupting of the semiconductor layer growth,wherein the forming of the first p-type semiconductor layer comprisessupplying a nitrogen gas to the substrate, wherein the interrupting ofthe semiconductor layer growth after forming the first p-typesemiconductor layer, comprises supplying a mixture of nitrogen gas andhydrogen gas to the substrate, and wherein the forming of the p-typecladding layer further comprises: switching carrier gas supply in theforming of the first p-type semiconductor layer and in the interruptingof the semiconductor layer growth after the forming of the first p-typesemiconductor layer.